1. Field of the Invention
The present invention relates to a tread for a tire for a heavy vehicle and more particularly to the tread pattern of such a tread for a tire intended to be mounted on a drive axle.
2. Related Art
In order to ensure both satisfactory grip and good clearing of water when driving over a roadway covered with water it is necessary to form on a tread a more or less complex system of cuts comprising a plurality of grooves and of sipes. These cuts form a tread pattern design both on the surface referred to as the tread surface that is intended to come into contact with the roadway and within the thickness of the tread.
Patent document FR 1452048 notably discloses how to form wide cuts (grooves) and narrow cuts (sipes). The latter have widths suited to their being able to close up as they enter the contact patch in which the tire is in contact with the roadway. Thus it is possible to benefit from the presence of edge corners while at the same time maintaining sufficient stiffness. A person skilled in the art has therefore to combine a necessary water-clearing volume, consisting of the volumes of voids formed notably by the grooves, with lengths of active edge corners comprising both the edge corners of the grooves and of the sipes.
Publication WO2010/072523-A1 also discloses how to form a reduced void volume when new, this void volume comprising parts intended to form new grooves once a part-worn condition is reached, these void volumes being connected to the grooves formed from new by a plurality of transverse sipes.
Document WO2013/150143 A1 describes a tire for an off-road vehicle comprising a tread in which the overall volume void ratio when new is at most equal to 15% and in which a middle region delimited by circumferential grooves has a void ratio of less than 10%.
The need has arisen to improve further the balancing act between total void volume when new and the lengths of active edge corners in the contact patch, and to do so for different levels of wear.